ESP WROOM 02 with battery socket, does it need extra resistors to monitor 4.2v?

wvmarle:
It seems that your module has some circuit on it that scales the ADC to a 0-3.3V full scale.
So try switching those two resistors: Vcc - 4k7 - A0 - 15k - GND.

Will try that too tomorrow, right now I made a photo with the 2 resistors that I though ware used as a volt divider ...